Using proprietary methodologies, Alexion Antibody Technologies (AAT), has produced phage display libraries expressing human antibody fragments (Fab) directed against Venezuelan equine encephalomyelitis virus (VEEV) from immunized military personnel. These antibodies are strong candidates for use as immunotherapeutics in the treatment of individuals at-risk of exposure to VEEV, and to assess the human anti-VEEV antibody repertoire. Neutralizing antibodies, either raised by vaccination in animals or passively administered to animal hosts, have been shown to provide protection in animals against VEEV. Through a contract with AAT, two VEEV neutralizing Fab fagments, P3F5 and P3G1, will be converted into whole IgG for expression, purification, and characterization. Characterization will include epitope identification, as well as the in vitro and in vivo neutralizing capacity of the human Abs and will be performed in the CDC laboratory. A larger panel of human Fabs directed against VEEV will then be generated by performing more extensive screens of existing phage display antibody libraries as well as building a new phage display library from the bone marrow of additional military personnel with serum titer against TC-83 (VEEV vaccine strain). Newly isolated anti-VEEV Fabs will be characterized at CDC to compare the human anti-VEEV antibodiy repertoire to the murine anti-VEEV antibody repertoire as defined previously by the CDC using a well-defined panel of murine monoclonal antibodies.